Object-oriented DBMS requirements

The requirements on an object-oriented DBMS for management of information in a large, complex enterprise are presented. These requirements aid in the achievement of an environment characterized by data sharing, open architectures, application and data portability, and assurance of data integrity. They were defined from the point of view of a user of the DBMS; therefore they describe the expected functionality of the DBMS and do not specify the method of implementation to achieve this functionality. They encompass requirements on the data model, query and data manipulation languages, the system architecure, interfaces to the system, change management, and transaction management.     

Consequence-based structural design approach for black swan events

The metaphor of black swan refers to unpredictable events like 9/11, the Indian Ocean tsunami, or the Oklahoma City Federal Building bombing, that cause catastrophic consequences for structural system safety. The likelihood of occurrence for such unforeseen events cannot be estimated from the observed data or prognosticated by experts. The absence of event and likelihood information renders futile the application of usual risk-based methods for design. Therefore, a shift from the probabilistic approach to consequence-based structural design is necessary for coping with the unexpected demands. This is accomplished through the conceptual development of a system capacity oriented design approach, where structural members are designed for variable reliabilities based upon their contribution to causing adverse system consequences. Information about general structural integrity encoded in the stiffness matrix is applied, using member consequence factors ranging from 0 to 1, for determining a member’s contribution towards system response. The structural system is designed using member consequence factors as additional partial factors on the resistance side of the design equations. The consequence-based scheme does not need a triggering hazard event (or its likelihood) and is an apt structural design approach for black swan events.     

Recent Observations on Tin Pest Formation in Solder Alloys

The most recent observations of the response of bulk samples of several lead-free solder alloys, exposed to temperatures below the allotropic transition for tin for extended periods, are reported. Tin pest has been observed in Sn-0.5Cu, Sn-3.5Ag, Sn-3.8Ag-0.7Cu, and Sn-3.0Ag-0.5Cu alloys at both −18°C and −40°C. The process is slow and inconsistent, usually requiring several years, but may eventually result in complete disintegration of the sample. No tin pest was detected in Sn-Zn-3Bi or in the traditional Sn-37Pb solder alloy after exposure for up to 4 and 10 years, respectively. It is suggested that nucleation is affected by local composition and that extremely small amounts of either intentional solute or impurity are influential. Growth of tin pest is accompanied by a large volume change, and it is likely that stress relaxation ahead of the expanding grey tin front is a controlling factor. A stronger matrix would be more resistant in this case, and at the temperatures of exposure Sn-37Pb is stronger than either Sn-3.5Ag or Sn-0.5Cu. The absence of tin pest, to date, on actual joints is attributed to their restricted free surface area and the greater strength associated with very small samples.     

高速PCB中的过孔设计研究

传输线的不连续问题已成为当今高速数字设计研究的重点,尤其是高速多层板中的过孔结构。随着频率的增长和信号上升沿的变陡,过孔带来的阻抗不连续会引起信号的反射,严重影响系统的性能和信号完整性。文章运用全波电磁仿真软件HFSS,对多种过孔结构进行了全面的研究。通过建立三维物理模型,分析了过孔直径、过孔长度和多余的过孔短柱几种关键设计参数对高速电路的信号完整性的影响。     

高速电路中的信号完整性分析

随着嵌入式系统速度的提高,信号完整性(Signal Integrity,SI)问题受到越来越多的关注。由于信号质量不理想而造成系统崩溃的现象经常出现。结合系统设计中的实例,对高速信号传输的信号完整性问题作了较为详细的论述。在电路设计初期,通过PROTEL软件对和信号完整性进行分析,仿真结果指导PCB板的设计,可以有效地提高信号的完整性,极大地缩短设计周期,降低设计成本。     

Effect of plasma process-induced damage on bias temperature instability of MOSFETs

For a surface-channel n-MOSFET and a buried-channel p-MOSFET, the effect of plasma process-induced damage on bias temperature instability (BTI) was investigated. The gate oxide thickness, t_ox, of the test MOSFETs was 2.0, 3.0, or 4.5 nm. The shifts of threshold voltage V_th and of linear drain current I_dlin were measured after applying a BTI stress at a temperature of 125 °C. The measured shifts of V_th and I_dlin indicate that BTI on ultra-thin gate CMOS devices appears only in the form of SiO₂/Si interface degradation, and that the positive BTI for the n-MOSFET as well as the negative BTI for the p-MOSFET is important for the reliability evaluation of CMOS devices. Because of positive plasma charging to the gate, a protection diode was very efficient at reducing BTI for the p-MOSFET, but it was much less effective for the n-MOSFET.     

多层印制板叠层设计对信号完整性的影响研究

基于优化多层印制板叠层设计改进信号完整性的目的,提出了通过叠层设计中调整印制板各层导线宽度、基板厚度、填充层厚度和绝缘材料厚度4个参数值,以改变各层信号传输路径特性阻抗的方法,结合工程实例,通过在特性阻抗连续和阻抗不连续两种情况下仿真的对比试验,验证了叠层设计优化方法的有效性.     

高速数字设计中的反射分析

随着集成电路开关速度的提高以及PCB（Printed Circuit Board）板密度的增加,信号完整性问题已成为高速PCB设计必须关注的问题之一,对信号进行完整性分析已经成为高速数字电路设计中的一个必要环节。本文介绍了高速PCB设计中出现的信号完整性问题,对相关的时序、反射、串扰和地弹等问题进行了深入讨论,并利用Hyperlynx对其作了相应的仿真。根据以上研究的结果,比较了不同的端接策略,验证了解决方案的有效性,也进一步表明信号完整性分析对于高速PCB设计的重要性。     

早餐食品安全的社会性规制问题——基于网络曝光的33个事件分析

早餐对于国民健康有至关重要的意义,随着早餐种类愈加丰富,消费者如何选购健康、安全的早餐愈加困难。基于扎根理论,分析早餐市场混乱的深层原因,并探索通过食育来培养消费者食品安全意识的途径,以减少食品安全事件的发生。运用NVivo11软件对33个食品事件进行归纳分析,研究结果表明早餐市场混乱的浅层原因为食品安全法律体系不完善,深层原因为消费者食品安全意识薄弱,可通过社会规制从根本规范早餐市场:鼓励经营者诚信经营,进而合法经营;通过食育中的饮食教育提升国民食品安全意识,促进食品市场的有序性。     

Antibacterial mode of action of seed essential oil of Eleutherococcus senticosus against foodborne pathogens

This study investigated the antibacterial mechanism of action of the seed essential oil of Eleutherococcus senticosus (ESEO) against foodborne pathogenic bacteria. Preliminarily, the ESEO (1000 μg disc^?1) showed potential antibacterial effect as diameter of inhibition zones (12.0 ± 0.2–37.0 ± 2.0 mm) against the tested foodborne pathogens. The MIC and MBC values of ESEO against the tested bacteria were found in the range of 125–500 and 500–1000 μg mL^?1, respectively. At MIC concentration, the ESEO had potential inhibitory effect on the cell viability of the tested pathogens. In addition, SEM analysis showed the inhibitory effect of ESEO as confirmed by considerable morphological alterations on the cell wall of B. cereus ATCC 13061 and E. coli O157:H7 ATCC 43889. Moreover, the ESEO revealed its mode of action against foodborne pathogens on membrane integrity as confirmed by release of extracellular ATP, 260‐nm absorbing materials and leakage of potassium ions. These findings confirm that the ESEO can be used as a potential antibacterial agent in food industry to inhibit the growth of various foodborne pathogens.